1. Field of the Invention
The present invention relates to an eye opening detection system for detecting eye openings of a detected subject and a method thereof.
2. Description of the Related Art
The eye opening detection system described in Japanese Patent No. 3383594 uses a technique for detecting the upper edge of a lower eyelid and then detecting the lower edge of the upper eyelid of a subject. The system described in Japanese Patent No. 3383594 scans pixels on a measuring line from the range where a threshold value for the detection of an iris edge point is acquired to the lower direction at first and detects the upper edge of the lower eyelid as a pixel position that density exceeds the threshold value for the detection of the iris edge point. Also, the system scans pixels on a measuring line from an upper edge of a pupil to the upper side thereof and detects the lower edge of the upper eyelid as a pixel position that density exceeds the threshold value for the detection of the iris edge point. Here, the threshold value for the detection of the iris edge point is set based on the maximum value of the density detected by the scanning from the lower edge of the pupil to the lower direction.
Although it is necessary to detect the upper and the lower eyelids for the detection of the eye opening of a detected subject, the lower eyelid has fewer characteristics in shape than the upper eyelid, and therefore, it is more difficult to detect the lower eyelid. The invention described in Japanese Patent No. 3383594 detects the lower eyelid first and then detects the upper eyelid, and consequently it may lead to a false detection of the lower eyelid and deterioration in a detection accuracy of the eye opening.